Reverse buckle sheet feeding apparatus

ABSTRACT

A reverse buckle sheet feeding apparatus is provided for feeding individual sheets from a stack. The apparatus includes a means for supporting the stack such as a tray or paper cassette, a feeding means for contacting the top sheet of the stack to advance it first rearwardly to form a buckle and then forwardly to feed the top sheet from the stack. A restraining means is preferably provided for preventing the rearward movement of the trailing edge of the top sheet as well as a contraining means for constraining the buckle. The constraining means causes the buckle to form between the constraining means and the trailing edge of the sheet and also serves to limit its size so as to increase the buckling force required and thereby substantially reduce multifeeding. The constraining means preferably comprises buckle control pads having a plurality of bristles extending outwardly therefrom and contacting opposing sides of the stack. Preferably the bristles are angled downwardly toward the top sheet of the stack.

United States Patent [1 Sanchez et al.

[ 1 REVERSE BUCKLE SHEET FEEDING APPARATUS [75] Inventors: Hector J. Sanchez, Webster; Donald W. Tates, Fairport, both of NJ.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: .Ian. 16, 1974 [21] Appl. No.: 433,623

Related US. Application Data [63] Continuation of Ser. No. 352,131, April 18, 1973,

11 3,893,663 [451 July 8,1975

Primary ExaminerRichard A. Schacher Assistant Examiner-Bruce H. Stoner, Jr.

Attorney, Agent, or Firm-James J. Ralabate; Clarence A. Green; Paul Weinstein [57] ABSTRACT A reverse buckle sheet feeding apparatus is provided for feeding individual sheets from a stack. The apparatus includes a means for supporting the stack such as a tray or paper cassette, a feeding means for contacting the top sheet of the stack to advance it first rearwardly to form a buckle and then forwardly to feed the top sheet from the stack. A restraining means is preferably provided for preventing the rearward movement of the trailing edge of the top sheet as well as a contraining means for constraining the buckle. The constraining means causes the buckle to form between the constraining means and the trailing edge of the sheet and also serves to limit its size so as to increase the buckling force required and thereby substantially reduce multi-feeding. The constraining means preferably comprises buckle control pads having a plurality of bristles extending outwardly therefrom and contacting opposing sides of the stack. Preferably the bristles are angled downwardly toward the top sheet of the stack.

23 Claims, 5 Drawing Figures REVERSE BUCKLE SHEET FEEDING APPARATUS This is a continuation of application Ser. No. 352,131, filed Apr. I8, 1973, now abandoned.

BACKGROUNU OF THE INVENTION This invention relates to a sheet feeding device suitable for use in an automatic reproducing machine. for example, a xerographic copier. The apparatus of the invention is adapted to feed individual sheets successively from a stack to a suitable mechanism which is to operate on the sheets. The sheet feeding apparatus is of a type in which one sheet of the stack is reverse buckled to detach it from the other sheets and when so detached is fed from the stack. In accordance with this invention means are included in the apparatus for constraining the buckle.

In a reverse buckle sheet feeder the rear margin of the stack is supported against the rear wall of the sheet support tray, so that the sheets are free to move only in a forward direction. Feeding means are then brought into operative contact with the upper most sheet in the stack and a motion imparted to the sheet to first drive the sheet rearwardly against the restraining force of the rear wall of the tray. As a consequence, a longitudinal buckle is formed in the body of the sheet causing the sheet to be separated from the stack. Once separated the direction of the sheet motion is reversed and the sheet is advanced forwardly through an opening in the tray and cleared therefrom prior to instituting a subsequent feeding cycle.

Although reverse buckle feeding as exemplified by the sheet feeding mechanism, disclosed in U.S. Pat. No. 3,645,615 to Spear, represents a reliable method of separating and forwarding individual sheets from a stack, it nevertheless has certain drawbacks. It has been found that reverse buckle type sheet feeders can be subject to frequent multi-feeding which is the feeding of two or more sheets at a time rather than the single sheet desired. Multi-feeding is particularly troublesome in a xerographic copier since it can lead to paper jams and premature shutdown of the copier. It is also a major problem when the copier is to be used to perform duplex copying. In this type of copying, originals may be first copied on one side of each sheet of final support material. and then the sheets are re-stacked, turned over and re-fed through the machine to copy on the other side. When duplex copying from sequenced originals, multi-feeding cannot be tolerated if the sequence is to be maintained.

SUMMARY OF THE INVENTION In accordance with this invention a reverse buckle paper feeder for feeding individual sheets of paper from a paper stack to, for example, a means for transferring an image thereto has been developed which markedly reduces the occurrence of multi-feeds as compared to prior art devices. The apparatus includes means for supporting the stack of paper. A feeding means is provided to contact the top sheet of the stack for advancing it first rearwardly to form a buckle, and then forwardly to feed the top sheet from the stack and preferably to an image transferring means. A restraining means is preferably provided to contact the trailing edge of the top sheet for preventing its rearward movement when the top sheet is being advanced rearwardly. A constraining means is provided between the feeding means and the restraining means. The constraining means contacts the opposed side edges of the stack for maintaining contact between the top sheet and a next adjacent sheet of the stack over a region between the feeding means and the restraining means. The constraining means is structured to permit substantial free movement of the top sheet in the forwardly and rearwardly feeding directions while at the same time maintaining the contact of the first and second sheets as above noted. The effect of the constraining means is to constrain the buckle to the rear portion of the sheet and to substantially reduce the size of the buckle and thereby increase the buckling force which has to be employed.

In accordance with the apparatus of this invention the buckling force is increased without necessitating a consequent increase in the required normal force between feeding means and the top sheet of the stack. Thereby a substantial reduction in multi-feeding is obtained.

The buckle in accordance with this invention forms between the constraining means and the trailing edge of the sheet which abuts the restraining means. The feeding means can be of a conventional design and preferably a roll type feeder is employed. The restraining means preferably comprise kick blocks which contact the trailing edge of the top sheet at the corners. The constraining means preferably comprises buckle control pads disposed on either side of the stack is opposing relationship at a point between the feeder and the kick blocks. The buckle control pads have outwardly extending bristles and the bristles are arranged to engage the uppermost sheet in the stack and to hold the sheet in contact with the next adjacent sheet thereto. The bristles of the pad are preferably oriented so that they extend outwardly and are angled toward the bottom of the stack. The use of pads having bristles oriented in this manner permits the stack to be easily placed into the support tray.

It is, therefore. an object of this invention to provide a sheet feeding apparatus which is adapted to substantially reduce the occurrence of multLfeeding.

It is a further object of this invention to provide an apparatus as above which comprises a reverse buckle type sheet feeder and wherein means are provided to constrain the buckle.

It is a further object of this invention to provide an apparatus as above wherein the constraining means comprises pads having a plurality of bristles extending outwardly therefrom the pads being disposed on opposing sides of the paper stack.

These and other objects will become more apparent from a consideration of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows schematically an exemplary xerographic copier with which the sheet feeder of this invention could be employed.

FIG. 2 shows a perspective view of a sheet feeding apparatus in accordance with this invention.

FIG. 3 shows a side view of the apparatus of FIG. 2 in partial cross-section.

FIG. 4 shows a perspective view of an exemplary buckle control pad in accordance with this invention.

FIG. 5 is a perspective view showing the engagement between a buckle control pad and the stack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 there is shown by way ofex ample an automatic xerographic reproducing machine which incorporates the improved sheet feeding appara tus of the present invention. The reproducing machine depicted schematically in FIG. 1 illustrates the various components utilized therein for producing copies from an original. Although the sheet feeding apparatus of the present invention is particularly well adapted for use in an automatic xerographic reproducing machine it should become evident from the following description that it is equally well suited for use in a wide variety of machines requiring single sheet feeding and is not necessarily limited in its application to the particular embodiment shown herein.

The reproducing machine illustrated in FIG. 1 cmploys an image recording drum-like member 10 the outer periphery of which is coated with a suitable photoconductive material 11. One type of suitable photoconductive material is disclosed in U.S. Pat. No. 2,970,906. issued to Bixby in 1961. The drum 10 is suitably journaled for rotation within a machine frame (not shown) by means of a shaft 12 and rotates in the direction indicated by arrow 13, to bring the image retaining surface thereon past a plurality of xerographic processing stations. Suitable drive means (not shown) are provided to power and coordinate the motion of the various cooperating machine components whereby a faithful reproduction of the original input scene information is recorded upon a sheet of final support material such as paper or the like.

Since the practice of xerography is well known in the art, the various processing stations for producing a copy of an original are herein represented in FIG. 1 as blocks A to E. Initially, the drum 10 moves photoconductive surface it through charging station A. At charging station A an electrostatic charge is placed uniformly over the photoconductive surface 11 of the drum l preparatory to imaging. The charging may be provided by a corona generating device of a type described in U.S. Pat. No. 2,836,725 issued to Vyverberg in 1958.

Thereafter the drum is rotated to exposure station B where the charged photoconductive surface 11 is exposed to a light image of the original input scene infor mation, whereby the charge is selectively dissipated in the light exposed regions to record the original input scene in the form ofa latent electrostatic image. A suitable exposure system may be of the type described in U.S. Patent Application, Serv No. 259,l8l. filed June 2, 1972, now U.S. Pat. No. 3,832,057, granted Aug. 27, 1974.

After exposure, drum 10 rotates the electrostatic latent image recorded on the photoconductive surface I l to development station C, wherein a conventional de veloper mix is applied to the photoconductive surface 11 of the drum l0 rendering the latent image visible. A suitable development station is disclosed in U.S. Patent Application Ser. No. 199,481 filed Nov. 17, 1971 now abandoned. The application describes a magnetic brush development system utilizing a magnitizable developer mix having carrier granuales and a toner colorent. The developer mix is continually brought through a directional flux field to form a brush thereof. The electrostatic latent image recorded on photoconduo tivc surface ll is developed by bringing the brush of developer mix into Contact therewith.

The developed image on the photoconductive surface 1 l is then brought into contact with a sheet of final support material 14 within a transfer station D and the toner image is transferred from the photoconductive surface 11 to the contacting side of the final support sheet 14. The final support material may be paper, plastic, etc. as desired.

After the toner image has been transferred to the sheet of final support material 14, the sheet with the image thereon is advanced to a suitable fuser 15 which coalesces the transferred powdered image thereto One type of suitable fuser is described in U.S. Pat. No. 2,701,765 issued to Codichini et al. in 1955. After the fusing process, the final support material 14 is advanced by a series of rolls 16 to a catch tray 17 for subsequent removal therefrom by the machine operator.

Although a proponderence of the toner powder is transferred to the final support material 14, invariably some residual toner remains on the photoconductive surface 11 after the transfer of the toner powder image to the final support material 14. The residual toner particles remaining on the photoconductive surface 11 after the transfer operation are removed from the drum 10 as it moves through cleaning station E. Here the residual toner particles are first brought under the influence of a cleaning corona generating device (not shown) adapted to neutralize the electrostatic charge remaining on the toner particles. The neutralized toner particles are then mechanically cleaned from the photoconductivc surface 11 by conventional means as for example. the use of a resiliently biased knife blade as set forth in U.S. Pat. No. 3,660,863 issued to Gerbasi in 1972.

It is preferred in accordance with this invention that the sheets of final support material 14 processed in the automatic xerographic reproducing device will be stored in the machine within a removable paper cassette 18. A suitable paper cassette is set forth in U.S. Patent Application Ser. No. 208,l38, filed Dec. 15, 1971, now US. Pat. No. 3,767,!87, granted Oct. 28, 1973.

The copier in accordance with this invention can also have the capability of accepting and processing copying sheets of varying lengths. The length of the copy sheet, of course, being dictated by the size of the original input scene information recorded on the photoconductive surface 11. To this end the paper cassette 18 is preferably provided with an adjustable feature whereby sheets of varying length and width can conveniently be accommodated therein.

In operation, the cassette 18 is filled with a stack of final support material 19 of pie-selected size and the cassette 18 is inserted into the machine by sliding along a base plate (not shown) which guides the cassette 18 into operable relationship with a pair of feed rollers 20. When properly positioned in communication with the feed rollers 20 the top sheet of the stack 19 is separated and forwarded from the stack 19 into the transfer station D by means of registration rolls 21.

It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an automatic xerographic copier which can embody the teachings of the present invention.

Referring now to FIG. 2, there is shown a reverse buckle sheet feeding apparatus in accordance with this invention. The apparatus includes means 31 for supporting a stack of paper. The supporting means 31 preferably comprises an adjustable tray as shown or a cassette as set forth in US. Application Ser. No. 208,138, filed Dec. l5, 197l, now US. Pat. No. 3,767,187, granted Oct. 23, I973. The tray 31 includes a bottom portion 32 which is adapted to support a stack 19 of final support material 14 such as paper or the like. Connected to the bottom portion 32 are adjustable side walls 33 and 34 which may be locked in a desired position by any conventional means such as holddown screws 35. The side walls 33 and 34 have protuberances 36 which contact the opposed sides 37 and 38 of the stack 19 and serve to guide the final support ma terial 14 as it is fed from the tray 31. Each of the side walls 33 and 34 includes a rear wall portion 40 and 41 respectively which cooperate to define the rear wall 42 of the tray 31.

A sheet feeding means 50 is provided which contacts the top sheet 51 of the stack 19 and advances it first rearwardly to form a buckle 52 as shown, and then forwardly to feed the sheet 51, for example, to an image transferring means such as station D in FIG. 1. The feeding means 50 may be of any conventional design as are well known in the art of reverse buckle feeding. The feeding means 50 shown comprises a pair of feed rolls 53 which are journaled for rotation and driven by conventional means (not shown). One particularly effective feeding means is shown and described in US. Application Ser. No 255,355, filed May 22, 1972, now US. Pat. No. 3,773.3!6, granted Nov. 20, 1973.

A restraining means 60 is preferably provided at the rear wall 42 of the support tray 31. The restraining means 60 contacts the trailing edge of the sheets in the stack 19, particularly, the trailing edge of the top sheet 51 for preventing its rearward movement when the top sheet is being advanced rearwardly. Preferably, the restraining means comprises kick blocks 61 and 62 positioned at the corners of the stack 19. The kick blocks ensure that normal loads and other forces applied to the top sheet 51 do not disengage the trailing edge of the sheet 51 from the rear wall 42 thereby preventing buckling thereof. The kick blocks 61 and 62 are adapted to have one surface 63 thereof in engagement with portions of the trailing edge of the sheet 51. Only the kick blocks 61 and 62 engage the trailing edge of the sheet 51, the remainder of the rear wall 42 is spaced therefrom.

In the preferred construction surface portions 63 have a textured sandpaper finish molded therein or secured thereto, i.e., about 80 grit finish. The textured finish increases the frictional forces of the surface por tions 63 to retain the trailing edge of the top sheet 51 in engagement therewith when the feeding means 50 moves the top sheet 51 in the direction of the rear wall 42 which for purposes of this invention is defined as a rearwardly movement. Texturing of surfaces 63 is but one means for ensuring that the trailing edge of the top sheet 51 of the stack 19 remains in contact therewith when the sheet 51 is being moved rearwardly. One skilled in the art would readily appreciate that the in vention is not necessarily so limited. For example, each surface portion 63 may have a lip extending therefrom over the top sheet 51 to ensure that it does not slide thereover when being moved rearwardly.

In the tray as set forth in FIG. 2, the protubrances 36 on each side wall 33 and 34 provide an air channel between each side wall and the opposed sides 37 and 38 of the stack 19. The kick blocks 61 and 62 in the rear wall 42 form a similar air channel. Air passes downwardly between the side walls 33 and 34 and the opposed side edges 37 and 38 of the stack 19 and between the rear wall 42 and the trailing edges of the stack 19 to prevent the formation of a partial vacuum therebetween and thereby facilitate sheet separation.

It has been found in accordance with this invention that the occurrence of multi-feeding is directly related to the ratio of the sheet buckling force to the feeder normal force. The sheet buckling force (Fb) is the force required to buckle the top sheet 51 of the stack 19. The feeder normal force (Fn) is the normal force exerted by the feed rollers 53 on the top sheet 51 of the stack 19. It has been found desirable to keep the ratio Fb/Fn as high as possible in order to substantially reduce the occurrence of multi-feeding.

This can be accomplished by either lowering Fn or raising Fb. If the normal force Fn is lowered the reliability of the feeding is adversely affected and the sheets 51 may not be fed at all. Therefore, increasing the buckling force Fb to increase the aforenoted ratio is the only practical means available for reducing the occurrence of multi-feeding.

Experience has shown that increasing the buckling force Fb by extending the area of the kick blocks 61 and 62 behind the stack 19 requires a proportional increase in the normal force Fn to prevent misfeeding. Therefore, the ratio Fb/Fn would remain practically the same. In accordance with this invention it has been determined that the preferred way to increase the ratio Fb/Fn is by increasing the buckling force Pb in the immediate area where the buckle takes place.

Therefore, each of the side walls 33 and 34 includes a constraining means which comprise buckle con trol pads 71. Preferably the buckle control pads 71 are located in opposing relationship on the side walls 33 and 34.

The constraining means 70 extend out past the protuberances 36 and contact the opposed sides 37 and 38 of the stack 19 and are operable to maintain substantial contact between the top sheet 51 of the stack and a next adjacent sheet 54 over a region between the feeding means 50 and the constraining means 70 during the feeding operation. The constraining means 70 are unique in that while maintaining the aforenoted contact, between the top sheet 51 and the next adjacent sheet 54, they permit substantially free movement of the top sheet 51 and the forwardly and rearwardly feeding direction.

Therefore, in accordance with this invention as shown in FIG. 3, the buckle 52 is formed between the constraining means 70 or buckle control pads 71 and the trailing edge of the sheet which abuts the restraining means 60 or the kick blocks 61 and 62.

The constraining means 70 in accordance with this invention preferably comprises buckle control pads 71 formed of a material, comprising as shown in FIG. 4, a backing member 72 having bristles 73 extending outwardly therefrom and angled with respect to the plane of the backing member 72. When the buckle control pads 71 are employed in the apparatus of FIG. 2, the bristles 73 are oriented such that they are angled downwardly toward the bottom of the stack 19 or toward the bottom 32 of the support tray 31. In this manner it is relatively easy to place a new stack 19 of final support material into the tray 31, since the bristles 73 are oriented in a direction which does not oppose the introduction of the new stack 19. Those bristles 73 engaged by the sides 37 and 38 of the stack 19, as shown in FIG. 5, are substantially flattened against the backing member 72, while those bristles 73 extending out above the stack 19 extend out over the edge of the top sheet 51 in the angular fashion shown. The bristles 73 are angled down towards the top sheet 51. Therefore, the buckle control pads 71 in accordance with this invention are highly effective for preventing separation of the top sheet 51 from the stack 19 in the region between the pads 71 and the feeder 50, but do not hinder the placement of the stack 19 in the tray 31. When the feed rolls 53 are rotated to advance the top sheet 51 rearwardly the top sheet 51 is free to so move even though it is constrained into contact with the next adjacent sheet 54 between the feed rolls 53 and the buckle control pads 71.

The buckle control pads 71 in accordance with this invention may be formed of any desired material and preferably have a structure similar to that shown in FIG. 4, namely, a backing member 72 with bristles 73 extending outwardly therefrom, and preferably oriented as shown. A particularly useful material for the buckle control pads 71 is FIBRE-TRAN linear drive facing, manufactured by the 3M Company, St. Paul, Minnesota. This product comprises a backing member 72 with 200 denier oriented nylon bristles 73 substantially as set forth in FIG. 4.

The constraining means 70 of this invention functions differently from drag pads used in prior art sheet feeders since they are not biased against the sides 37 and 38 of the stack 19 by spring means or the like. Further, they do not serve to inhibit the substantially free movement of the sheets 14 of the stack 19 in the forwardly and rearwardly feeding directions. The use of a material such as nylon or other suitable resin type material for the constraining means 70 provides a much lower coefficient of friction between the sheets 14 and the constraining means 70 and hence a much lower frictional drag on the sheets 14 than materials such as rubber or cork commonly used for drag pads.

The frictional drag exerted by drag pads on the edges of the sheets 14 of the stack 19 is the mechanism by which they provide sheet separation during feeding. In contrast thereto, the constraining means 70 of this invention are operative to constrain the buckle by preventing separation of the top sheet 51 from the next adjacent sheet 54 over the region between the feed means 50 and the constraining means 70, while not exerting a substantial frictional drag on the edges of the sheets 51 and 54.

It is preferable that the buckle control pads 71 contact the opposed edges 37 and 38 of the stack 19 at about the same distance from respective kick blocks 61 and 62 since this provides a uniform buckle 52. However, some misregistration or difference in the respective distances from the kick blocks61 and 62 of the buckle control pads 71 on the respective sides 37 and 38 of the stack 19 can be tolerated. Preferably any such misregistration is on the order of 1 inch or less and more preferably less than about one-half inch. Such misregistration can occur when one of the buckle control pads 70 is secured to an adjustable paper guide as in the cassette of US. Patent Application Ser. No. 208,138 filed Dec. I5, 1971, now US. Pat. No. 3,767,187 granted Oct. 23, I973 Preferably the buckle control pads 71 are positioned less than about 3 inches, and more preferably from about 1 inch to about 2% inches from the kick blocks 61 and 62. When the pads 71 are so positioned the buckle S2 is sufficiently small to provide the requisite increase in the buckling force to substantially reduce multi-feeding A lower limit is imposed on the width of the buckle 52 due to the fact that too small a buckle 52 can crease or otherwise damage the sheets. Buckle control pads 71 positioned 1% inches from the kick blocks 61 and 62 have been found to be highly effective in preventing multi-feeding.

The width of the buckle control pads 71 as measured in the feeding direction may be set as desired but preferably is less than about one-half inch. A A inch wide pad has been found to be highly effective in preventing mulit-feeds. The height of the pads 71 should be sufficiently great so that some of the bristles 73 extend over the top sheet 51.

Referring again to FIG. 5, it is evident that the buckle control pads 71 provide a substantially continuous constraint on the size of the buckle 52 even as the stack is depleted. As the sheets are fed from the stack bristles 73 which had been deformed against the backing member 72 are released and spring out over the newly surfaced top sheet 51 thereby providing substantially continuous series of constraints.

The term stack as employed in this application refers to a pile of sheets. The sheets may be original documents or final support material as desired.

The patents and applications referrred to specifically in the detail description of this application are intended to be incorporated by reference into the description.

Therefore it is apparent that there has been provided in accordance with this invention a reverse buckle sheet feeding apparatus which fully satisfies the objects, aims and advantages set forth hereinbefore. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

What is claimed is:

1. A reverse buckle sheet feeding apparatus for feeding individual sheets from a stack comprising:

means for supporting said stack, said stack having a plurality of individual sheets, each of said sheets having side edges in opposing relationship, a leading edge and a trailing edge;

feeding means adapted to contact the top sheet of said stack for advancing it first rearwardly to form a buckle and then forwardly to feed said top sheet from said stack", and

means for constraining said buckle for limiting the size of said buckle, said constraining means being located between said feeding means and the trailing edge of said top sheet, said constraining means being adapted to contact said opposed side edges of said sheets of said stack, said constraining means permitting substantially free movement of said top sheet in the forwardly and rearwardly feeding directions;

whereby said buckle forms between said constraining means and the trailing edge of said top sheet during feeding. and the size of said buckle is reduced as compared to an unconstrained buckle.

2. A sheet feeding apparatus as in claim I wherein, said constraining means maintains substantial contact between said top sheet and a next adjacent sheet of said stack over a region between said feeding means and said constraining means.

3. A sheet feeding apparatus as in claim 2 wherein, said constraining means comprises buckle control pads, and wherein said buckle control pads have a plurality of bristles extending outwardly over said top sheet.

4. A sheet feeding apparatus as in claim 3 wherein, said bristles of said buckle control pad are angled such that they extend outwardly and downwardly toward said top sheet.

5. A sheet feeding apparatus as in claim 3 wherein, said means for supporting said stack comprises a tray having a bottom portion, sidewalls in opposing relationship, and a rear wall, said stack being adapted to fit within the confines of said side walls and said rear wall and to be supported by said bottom portion.

6. A sheet feeding apparatus as in claim 5 wherein, said buckle control pads comprise a backing member and said bristles extend out from said backing members and are angled with respect to the plane of said backing member so that they extend toward said bottom portion of said tray, said pads being affixed to said side walls of said tray.

7. A sheet feeding apparatus as in claim 6 wherein, at least one of said sidewalls of said tray is adjustable to conform to sheets of varying sizes.

8. A reverse buckle sheet feeding apparatus for feeding individual sheets of final support material from a stack to a means for transferring an image thereto, comprising:

means for supporting said stack of final support material, said stack having a plurality of individual sheets, each of said sheets having side edges in opposing relationship a leading edge and a trailing edge;

feeding means adapted to contact the top sheet of said stack for advancing it first rearwardly to form a buckle and then forwardly to feed said top sheet to said image transferring means;

restraining means adapted to contact said top sheet for preventing the rearward movement of said trailing edge once said top sheet is being advanced rearwardly, and means for constraining said buckle for limiting the size of said buckle, said constraining means being adapted to contact said opposed side edges of said sheets of said stack, said constraining means being located between said feeding means and said restraining means, said constraining means permitting substantially free movement of said top sheet in the forwardly and rearwardly feeding directions;

whereby said buckle forms between said constraining means and said restraining means during feeding, and the size of said buckle is reduced as compared to an unconstrained buckle.

9. A sheet feeding apparatus as in claim 8 wherein, said constraining means maintains substantial contact between said top sheet and a next adjacent sheet of said stack over a region between said feeding means and said constraining means.

10. A sheet feeding apparatus as in claim 9 wherein, said constraining means comprises buckle control pads, and wherein said buckle control pads have a plurality of bristles extending outwardly over said top sheet.

ll. A sheet feeding apparatus as in claim 10 wherein, said bristles of said buckle control pad are angled such that they extend outwardly and downwardly toward said top sheet.

12. A sheet feeding apparatus as in claim 10 wherein, said means for supporting said stack comprises a tray having a bottom portion, sidewalls in opposing relationship, and a rear wall, said stack being adapted to fit within the confines of said side walls and said rear wall and to be supported by said bottom portion.

13. A sheet feeding apparatus as in claim 12 wherein, said buckle control pads comprise a backing member and said bristles extend out from said backing members and are angled with respect to the plane of said backing member so that they extend toward said bottom portion of said tray, said pads being affixed to said side walls of said tray.

14. A sheet feeding apparatus as in claim 13 wherein, at least one of said sidewalls of said tray is adjustable to conform to sheets of varying sizes.

15. A sheet feeding apparatus as in claim 14 wherein, said restraining means comprises kick blocks affixed to said rear wall so as to contact the trailing edge of said top sheet at the corners thereof, said kick blocks having a textured operative surface which contacts said trailing edge.

16. A sheet feeding apparatus as in claim 15 wherein, the distance between said buckle control pad and said surface of said kick block at one side wall is within about 1 inch of the distance between said buckle control pad and said surface of said kick block at said opposing side wall.

17. A sheet feeding apparatus as in claim 16 wherein, the distances between each of said buckle control pads and each of said surfaces of said kick blocks is substantially the same.

18. A sheet feeding apparatus as in claim 16 wherein, said buckle control pads are positioned less than about 3 inches from said surfaces of said kick blocks.

19. A sheet feeding apparatus as in claim [8 wherein, said buckle control pads are positioned from about I inch to about 2% inch from said surfaces of said kick blocks.

20. A sheet feeding apparatus as in claim 19 wherein, said buckle control pads are less than about 9% inch wide as measured in the direction of feeding.

21. A sheet feeding apparatus as in claim 20 wherein, said bristles of said buckle control pads are formed of nylon.

22. A sheet feeding apparatus as in claim 2] wherein, said feeding means comprises at least one roller.

23. A sheet feeding apparatus as in claim 8 wherein, said image transferring means comprises an automatic xerographic reproducing machine. i 

1. A reverse buckle sheet feeding apparatus for feeding individual sheets from a stack comprising: means for supporting said stack, said stack having a plurality of individual sheets, each of said sheets having side edges in opposing relationship, a leading edge and a trailing edge; feeding means adapted to contact the top sheet of said stack for advancing it first rearwardly to form a buckle and then forwardly to feed said top sheet from said stack; and means for constraining said buckle for limiting the size of said buckle, said constraining means being located between said feeding means and the trailing edge of said top sheet, said constraining means being adapted to contact said opposed side edges of said sheets of said stack, said constraining means permitting substantially free movement of said top sheet in the forwardly and rearwardly feeding directions; whereby said buckle forms between said constraining means and the trailing edge of said top sheet during feeding, and the size of said buckle is reduced as compared to an unconstrained buckle.
 2. A sheet feeding apparatus as in claim 1 wherein, said constraining means maintains substantial contact between said top sheet and a next adjacent sheet of said stack over a region between said feeding means and said constraining means.
 3. A sheet feeding apparatus as in claim 2 wherein, said constraining means comprises buckle control pads, and wherein said buckle control pads have a plurality of bristles extending outwardly over said top sheet.
 4. A sheet feeding apparatus as in claim 3 wherein, said bristles of said buckle control pad are angled such that they extend outwardly and downwardly toward said top sheet.
 5. A sheet feeding apparatus as in claim 3 wherein, said means for supporting said stack comprises a tray having a bottom portion, sidewalls in opposing relationship, and a rear wall, said stack being adapted to fit within the confines of said side walls and said rear wall and to be supported by said bottom portion.
 6. A sheet feeding apparatus as in claim 5 wherein, said buckle control pads comprise a backing member and said bristles extend out from said backing members and are angled with respect to the plane of said backing member so that they extend toward said bottom portion of said tray, said pads being affixed to said side walls of said tray.
 7. A sheet feeding apparatus as in claim 6 wherein, at least one of said sidewalls of said tray is adjustable to conform to sheets of varying sizes.
 8. A reverse buckle sheet feeding apparatus for feeding individual sheets of final support material from a stack to a means for transferring an image thereto, comprising: means for supporting said stack of final support material, said stack having a plurality of individual sheets, each of said sheets having side edges in opposing relationship a leading edge and a trailing edge; feeding means adapted to contact the top sheet of said stack for advancing it first rearwardly to form a buckle and then forwardly to feed said top sheet to said image transferring means; restraining means adapted to contact said top sheet for preventing the rearward movement of said trailing edge once said top sheet is being advanced rearwardly, and means for constraining said buckle for limiting the size of said buckle, said constraining means being adapted to contact said opposed side edges of said sheets of said stack, said constraining means being located between said feeding means and said restraining means, said constraining means permitting substantially free movement of said top sheet in the forwardly and rearwardly feeding directions; whereby said bUckle forms between said constraining means and said restraining means during feeding, and the size of said buckle is reduced as compared to an unconstrained buckle.
 9. A sheet feeding apparatus as in claim 8 wherein, said constraining means maintains substantial contact between said top sheet and a next adjacent sheet of said stack over a region between said feeding means and said constraining means.
 10. A sheet feeding apparatus as in claim 9 wherein, said constraining means comprises buckle control pads, and wherein said buckle control pads have a plurality of bristles extending outwardly over said top sheet.
 11. A sheet feeding apparatus as in claim 10 wherein, said bristles of said buckle control pad are angled such that they extend outwardly and downwardly toward said top sheet.
 12. A sheet feeding apparatus as in claim 10 wherein, said means for supporting said stack comprises a tray having a bottom portion, sidewalls in opposing relationship, and a rear wall, said stack being adapted to fit within the confines of said side walls and said rear wall and to be supported by said bottom portion.
 13. A sheet feeding apparatus as in claim 12 wherein, said buckle control pads comprise a backing member and said bristles extend out from said backing members and are angled with respect to the plane of said backing member so that they extend toward said bottom portion of said tray, said pads being affixed to said side walls of said tray.
 14. A sheet feeding apparatus as in claim 13 wherein, at least one of said sidewalls of said tray is adjustable to conform to sheets of varying sizes.
 15. A sheet feeding apparatus as in claim 14 wherein, said restraining means comprises kick blocks affixed to said rear wall so as to contact the trailing edge of said top sheet at the corners thereof, said kick blocks having a textured operative surface which contacts said trailing edge.
 16. A sheet feeding apparatus as in claim 15 wherein, the distance between said buckle control pad and said surface of said kick block at one side wall is within about 1 inch of the distance between said buckle control pad and said surface of said kick block at said opposing side wall.
 17. A sheet feeding apparatus as in claim 16 wherein, the distances between each of said buckle control pads and each of said surfaces of said kick blocks is substantially the same.
 18. A sheet feeding apparatus as in claim 16 wherein, said buckle control pads are positioned less than about 3 inches from said surfaces of said kick blocks.
 19. A sheet feeding apparatus as in claim 18 wherein, said buckle control pads are positioned from about 1 inch to about 2 1/4 inch from said surfaces of said kick blocks.
 20. A sheet feeding apparatus as in claim 19 wherein, said buckle control pads are less than about 1/2 inch wide as measured in the direction of feeding.
 21. A sheet feeding apparatus as in claim 20 wherein, said bristles of said buckle control pads are formed of nylon.
 22. A sheet feeding apparatus as in claim 21 wherein, said feeding means comprises at least one roller.
 23. A sheet feeding apparatus as in claim 8 wherein, said image transferring means comprises an automatic xerographic reproducing machine. 